Being among the powers and schools that can legitimately call themselves a blue blood of the sport is something that should be unquestioned when it comes to USC. It is something that does not have an official set of criteria.
In general, historic relevance and role throughout CFB history, as well as titles and the overall current state of the program, are factors that play into fans' debate of who to include or not. Certainly, when looking at the early 2000s and before, there is no one making a legitimate point that would question the Trojans' status.
Those dismissing the USC program are choosing to overemphasize some of the more recent years. To an extent, that is understandable. Recency bias and the last impression from something that just happened will inherently stand out more.
The ultimate litmus test in such conversations ultimately comes down to how much impact and reach a program has on the whole of the sport. If anything, the down years prove USC's place among the blue bloods.
Every fan, regardless of who they root for, knows what is going on within the Trojan program. Many love discussing and speculating as to what the future in Los Angeles will look like. When USC starts winning consistently at a high level again, that effect will only increase tenfold and become that much more noticeable.
Championships and winning can be cyclical. While Alabama enjoyed a long stint on top of college football, early returns are not looking promising, for example, that this will continue to be the case for the Crimson Tide without coach Nick Saban.
Return of USC prominence
The ultimate factor that too many are overlooking is the very real impact that the sanctions had. Only now is the program truly coming out from the other side of those NCAA restrictions. Now again on the same playing field, many are acting like the recruiting wins are some sort of fluke or that they are more or less meaningless.
What those voices are experiencing firsthand is the return of a true blue blood.